4. What is a mutation?

4.1 Definitions

Strictly speaking, a "mutation" is any sudden and permanent change in the somatic or hereditary (germline) genetic make-up, through a change in the number or quality of genes (genotoxicity):

• somatic mutagenesis acts on the body's own cells and may cause cancer;

• germline mutagenesis results in an alteration of the reproductive genetic material; it is transmitted to offspring;

• clastogenesis is characterized by chromosome breakage and loss of substance;

• chromosomal aberrations are random rearrangements of chromosome structure and/or number, which may affect the whole chromosome or only part of it (chromatic aberration)...